One problem area in photography is "macro" photos--photos taken at very close range. One area in which this problem often arises is the field of law enforcement. Specifically, law enforcement officials are often called upon to take 1:1 (actual size) photographs of evidentiary items. Fingerprint photos are the most common usage of 1:1 photography in this field.
The problem in this sort of picture taking arises because most cameras can only be focused to a distance of approximately three feet. For fingerprint photography, this is not acceptable.
Cameras can be modified, e.g. by the addition of a macro lens, so as to be able to focus at these close ranges, but it is still very difficult to hold the camera in the proper position to achieve a focused shot at a range of 3-4 inches.
Current art devices are limited in that they generally require, at the very least, a diopter lens to achieve proper focusing. This type of device leads to "vignetting" (fringe interference), and does not provide the quality sought for many applications.